The big dilemma of the drivers from all over the world: what car to buy, on gas or diesel? For many years this question is present in every driver’s mind, most of all when they decide to buy a car from import. Analyzing the sales statistics from the past years we notice that their preferences are, at least for the moment, equal: 50% are in favor of gas and the other 50% decide for diesel. Which are the pro and against arguments that helps a driver to take such a decision? The owners of gas cars declare that they will stick to their first love, the gas engine. When you ask them to justify their choice, some of them, without thinking to much, cite the all ready known details: has a more quick start, a lower level of pollution, vibration and noise, an easier acceleration and a larger domain of the revolutions. In the past years these qualities managed to be fully fulfilled even of the diesel engines: the run-up of the engine on cold weather is a lot better, the insulation of the engine was also improved. Another two reasons that can not be neglected for the engines on diesel: the lower consumption and the smaller price of the combustible. Lets make an estimation about the profitableness of using an diesel car that costs with 2.000 euros more then a car on gasoline. The medium consumption for a diesel is 4.8l/100 km while for gas is 7.2l/100 km. At the present prices 3.43 RON/ liter for gasoline and 3.34 RON/liter for diesel, at 100 covered km, the driver that has a diesel car spends 16.03 RON while the driver that has a gas car spends 24.7 RON. The difference of 8.67 RON allows us to assume that the 2000 euros extra paid for a diesel car will pay off after 83.300 covered km. So, only after 4 or 5 years of usage, after 20.000 km driven per year, the diesel becomes rentable. But after 5 years problem start to appear, increasing the costs. This situation is profitable for the transportation firms: a diesel that covers over 100.000 km/ year becomes more rentable at the end of the year then a car on gas. An even more interesting aspect is the one noticed at the car from a higher class where the difference of consumption is higher, the diesel becoming more rentable. A match-less efficiency is noticed at the big engines that use diesel: busses, coaches and trucks. For the moment, the diesel engines are efficient only for transporting firms that uses big cars, where the cost of the combustibles represents the most important part of the total expenses. But when we make these estimations, we must take into consideration not only the acquisition prices but also the after buying costs, meaning insurance, revision and maintenance. If we talk only about the spare parts, the costs are higher for a diesel engine. The pumps, injectors, rotary-blowers, filters of particles with catalyst and incandescent spark-plugs for the cold season cost almost double then the spare parts for gas engine (injectors, spark-plugs, petrol filter). And as a last argument: the growth of the world auto park with diesel engines contributed at the high request of diesel, and in many countries the price for a liter of diesel is almost the same as the price for a liter of gas, and very soon the advantage of the smaller price for diesel will disappear. But the dilemma will persist because there are advantages and disadvantages that we should know before deciding what car to buy. After you read our arguments what is your decision?